The present invention relates to an automatic focusing device for a video camera.
Recently, video cameras have come into wide use, and there have been available many video cameras having automatic focusing devices. A video camera with an automatic focusing device has a significant merit in that it is unnecessary to manually focus the lens on the object. In general, a conventional automatic focusing device is designed so that as soon as the camera becomes out of focus the device operates to return the camera quickly to the focused state. However, the conventional automatic focusing device is disadvantageous in that, when, for instance, an unwanted object passes between the lens and the target object (which occurs frequently in ordinary photographing operations), the device operates to focus the lens on the unwanted object, whereupon the target object becomes out of focus. Thus, the resultant picture appears unsatisfactory on the television screen.
In order to eliminate this problem of focusing on the unwanted object (hereinafter referred to as "a crossing object"), an automatic focusing device has been proposed in which the lens driving operation is suspended for a period of time required for the crossing object to completely move out of the photographing field. Such a conventional automatic focusing device can effectively eliminate the defocusing problem caused by the crossing object. However, the device suffers from other drawbacks in that, when the camera is panned, the response of the device is slow, and when an object moves towards or away from the camera, the device cannot follow the object at all.